Exploiting Alkylquinone Tautomerization for the Total Synthesis of Calothrixin A and B

J Org Chem. 2017 Dec 1;82(23):12257-12266. doi: 10.1021/acs.joc.7b02101. Epub 2017 Nov 17.

Abstract

The pentacyclic alkaloid calothrixin B (1) has been synthesized in 5 steps from murrayaquinone A (9). The key step involved the union of boryl aniline 31 with brominated murrayaquinone A (26). In this transformation, alkylquinone 26 undergoes tautomerization to a quinone methide, which is intercepted by boryl aniline 31 to forge a new C-N bond. An intramolecular Suzuki coupling, followed by dehydrogenative aromatization, completed the synthesis of calothrixin B. Subsequent N-oxidation of calothrixin B delivered calothrixin A. The successful synthesis of these alkaloids and the challenges that led to the development of the final synthesis plan are reported herein.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amination
  • Benzoquinones / chemistry*
  • Indole Alkaloids / chemical synthesis*
  • Indole Alkaloids / chemistry
  • Molecular Structure

Substances

  • Benzoquinones
  • Indole Alkaloids
  • calothrixin A
  • calothrixin B